Various kinds of analyzers that use an infrared radiation source, such as an infrared gas analyzer, have been provided. A typical infrared radiation source used in such an analyzer is a halogen lamp. However, the halogen lamp is large and has a relatively short life span, so it is difficult to apply it to a small gas sensor that detects gas using infrared rays.
So, as an infrared radiation source that can be miniaturized, an infrared radiation element formed by using a micro machining technology has been developed in many places (For example, see Japanese Non-examined Patent Publication No. 9-153640 (paragraphs [0027]-[0028], FIG. 2), Japanese Non-examined Patent Publication No. 2000-236110 (paragraphs [0017]-[0019], FIGS. 1 and 2), and Japanese Non-examined Patent Publication No. 10-294165 (paragraphs [0014]-[0015], FIG. 1)).
In the above patent documents, an infrared radiation element of a so-called micro-bridge structure is disclosed, which comprises a supporting substrate which is formed from a silicon substrate and so on by using a micro machining technology and in the form of a rectangular frame, and a wire heat generator across the supporting substrate. In the infrared radiation element having the micro-bridge structure of this kind, infrared rays are emitted from the wire heat generator by Joule heat generated by energization of the wire heat generator, and such an infrared radiation element can quickly respond to a on/off state of a current passing through the heat generator because the heat generator is surrounded by air and therefore heat capacity difference between the heat generator and its surroundings can be increased.
However, in the above infrared radiation element having the micro-bridge structure, the heat generator is subject to breakage, and it may be melted by the heat because the heat generator is in the form of a line, and only both ends of the heat generator are supported by the supporting substrate.